This invention relates generally to telecommunication systems, and more specifically to systems that convert communication signals for transmission between interconnected computers.
Traditionally, data transmission between two interconnected computers was accomplished through the use of analog telecommunication lines. Data communication over analog telecommunication lines could be accomplished by converting digital data into analog signals prior to transmission and converting the analog signals back into digital data upon receipt of the transmission.
The digital/analog conversion function is typically accomplished through a modulator/demodulator (MODEM). Thus, installing a first MODEM between the sending computer and the analog telecommunication line and a second MODEM between the analog telecommunication line and the receiving computer allows digital data to be transmitted using analog signals.
Recent advances in telecommunication technology have made it possible for telecommunication service providers to offer transmission lines which can facilitate the transmission of digital data. Digital data transmissions can be faster, more reliable and error-free than analog transmissions.
There are a number of types of digital telecommunication lines presently offered by telecommunication service providers. One type of telecommunication line that supports the transmission of digital data is commonly referred to in the industry as an integrated services digital network (ISDN) line.
In order to take advantage of an available digital telecommunication line, a computer must be adapted to provide a connection between the computer and the digital telecommunication line. Typically, this connectivity is achieved through the use of a personal computer terminal adapter (PCTA) which allows digital data to be input to and output from the computer.
In order to integrate the digital telecommunication lines into the existing system of analog transmission lines, telecommunication service providers implemented switching stations. These switching stations route transmissions to the appropriate lines and perform a translating function for transmission between analog and digital lines.
The translating function is performed using a Coder/Decoder (CODEC). To translate analog signals into digital data, for example, a CODEC receives analog signals transmitted along an analog telecommunication line, creates a coded digital representation of the analog signals, and transmits the coded digital representation of the analog signals along a digital telecommunication line.
There are several standard encoding schemes presently utilized to translate analog signals representing digital data into encoded digital data describing the analog signals representing digital data. The Mu law, ADPCM and the A law are examples of conversions methods well known in the art which are capable of performing such a translation.
Conversely, when data is being transmitted along a digital telecommunication line to be received using an analog telecommunication line, the switching station via the CODEC performs the reverse translation, namely converting coded digital data into analog signals.
Although switching stations facilitate the transmission of data between analog and digital telecommunication lines, the format of the coded digital data created by a CODEC is not compatible with standard computers. Consequently, a computer directly connected to a digital telecommunication line could not utilize the coded digital data without additional hardware.
Presently, a computer receiving coded digital data from a digital telecommunication line requires a second CODEC to decode the coded digital data to create an analog signal for transmission to a MODEM.
FIG. 1 illustrates the equipment currently necessary for data transmission between a standard personal computer and a public switched network using an analog telecommunication line. The digital data transmitted by the personal computer 100 via the data port 108 will hereinafter be referred to as application data.
In FIG. 1, a personal computer 100, having a keyboard 102, a monitor 104, a data port 108 and a program 106 capable of communicating with the data port 108 is attached to a MODEM 110. The MODEM 110 is connected to an analog telecommunication line 112 which is connected to a public switched network 114. The public switched network 114 has an attached CODEC 116 which can connect the analog telecommunication line 112 to a digital telecommunication line 118.
Application data to be transmitted from the personal computer 100 through the public switched network 114 is first passed from the program 106 through the data port 108 to the MODEM 110. The MODEM converts the digital data into analog signals capable of being transmitted along the analog telecommunication line 112.
The analog signals are routed by the public switched network 114 to the CODEC 116 which creates coded digital data representing the analog signals. The CODEC 116 transmits the coded digital data representing the analog signals out of the public switched network 114 along the digital telecommunication line 118.
Although the data transmission described above originates at the personal computer 100 and terminates after the coded digital data passes through the digital telecommunication line 118, data transmissions in the reverse direction are similarly accommodated. Regardless of the direction of the data transmission, the digital telecommunication line 118 carries coded digital data representing analog signals and the analog telecommunication line 112 carries analog signals.
FIG. 2 illustrates the equipment currently necessary for data transmission between a personal computer having an attached MODEM and CODEC and a public switched network using a digital telecommunication line.
In FIG. 2, a personal computer 200, having a keyboard 202, a monitor 204, a data port 208 and a program 206 capable of communicating with the data port 208 is attached to a MODEM 210. The MODEM 210 is connected to a terminal adapter (TA) 212. The TA 212 has an attached CODEC 214. The TA 212 is connected to a digital telecommunication line 216 which is connected to a public switched network 218.
Application data to be transmitted from the personal computer 200 through the public switched network 218 is first passed from the program 206 through the data port 208 to the MODEM 210. The MODEM converts the digital application data into analog signals capable of being transmitted along an analog telecommunication line.
The analog signals are transmitted from the MODEM 210 to the CODEC 214 attached to the TA 212. The CODEC converts the analog signals into coded digital data representing the analog signals. The coded digital data is transmitted from the TA 212 along the digital telecommunication line 216 to the public switched network 218.
After the public switched network 218 receives the coded digital data representing analog signals, the data can be transmitted out of the public switched network 218 using either a second digital telecommunication line or an analog telecommunication line with an attached CODEC as illustrated in FIG. 1.
Although the data transmission described above originates at the personal computer 200 and terminates after the coded digital data passes through the public switched network 218, data transmissions in the reverse direction are similarly accommodated. Regardless of the direction of the data transmission, the digital telecommunication line 216 carries coded digital data representing analog signals.
FIG. 3 illustrates the equipment currently necessary for data transmission between a personal computer having a TA with a rate adapter (RA) and a public switched network using a digital telecommunication line.
In FIG. 3, a personal computer 300, having a keyboard 302, a monitor 304, a TA 306 with an attached RA 308 and a program 310 capable of communicating with TA 306 is attached to a first digital telecommunication line 312. The rate adapter is a device known in the art for transmitting and receiving the bits of a low speed bit stream using a higher speed communication channel. The digital telecommunication line 312 is connected to a public switched network 314.
The public switched network 314 includes a terminal adapter 316 with an attached rate adapter 318, a MODEM 320, a CODEC 322 and a second digital telecommunication line 324.
Application data to be transmitted from the personal computer 300 through the digital telecommunication line 324 is first passed from the program 310 through the TA 306 and attached rate adapter 308 to the first digital telecommunication line 312. The digital data transmitted along the digital telecommunication line 312 is in a digital format adapted to flow at a rate compatible with both rate adapter 318 and rate adapter 308.
The digital data is received by the public switched network 314 and transmitted to terminal adapter 316 having rate adapter 318. Terminal adapter 316 utilizing rate adapter 318 converts the rate adapted digital data into digital data typically transmitted through an analog MODEM.
The digital data typically transmitted through an analog MODEM is transmitted from terminal adapter 316 to MODEM 320 which converts the digital data into analog signals. MODEM 320 transmits the analog signals to CODEC 322 which creates coded digital data representing the analog signals. CODEC 322 then transmits the coded digital data out of the public switched network 314 through digital telecommunication line 324.
Although the data transmission described above originates at the personal computer 300 and terminates after the coded digital data passes through the digital telecommunication line 324, data transmissions in the reverse direction are similarly accommodated. Regardless of the direction of the data transmission, the digital telecommunication line 312 carries rate adapted digital data, digital telecommunication line 324 carries coded digital data representing analog signals.
As illustrated by FIGS. 1-3, MODEMs and CODECs are currently necessary to accommodate the variety of telecommunication line types and digital transmission formats presently in use. MODEMS and CODECs are used both in conjunction with a communicating computer and within public switched networks.
Switching stations in public switched networks typically manage a large number of analog and digital telecommunication lines. Each switching station, therefore, requires a number of MODEMs and CODECs in order to convert between analog signals and coded digital data. These groups of MODEMs and CODECs within a public switched network are commonly referred to as MODEM pools.
A large number of MODEMs and CODECs are presently required by computers and public switched networks and data communications through public switched networks is increasing. A need, therefore, exists for a device which will directly convert between data typically transmitted through an analog MODEM and analog signals encoded for transmission over a digital telecommunication network, thus eliminating the need for additional special purpose hardware.
An object of the present invention is to provide an apparatus for transforming application data typically transmitted between applications through an analog MODEM into digital data encoded for transmission over a digital telecommunication network representing analog signals carrying application data. This conversion is typically performed using special purpose hardware. The present method and apparatus, however, employs control logic in conjunction with a computer for more efficient and cost-effective transmission than prior art solutions.
Another object of the present invention is to provide an apparatus for more efficiently using a digital telecommunication network which transforms analog signals into a format capable of being interpreted by control logic without necessitating additional hardware.
The foregoing objects are realized and a technical advance is achieved by the present invention. The apparatus of the present invention consists of a computer having a processor and memory. The computer must also have control logic and a communications interface device for transmitting and receiving application data. The control logic of the computer is used to transform application data typically transmitted between applications using an analog MODEM to and from digital data encoded for transmission over a digital telecommunication network representing analog signals carrying application data.
The apparatus of the present invention comprises the communications hardware, memory, CPU and control logic to receive input of digital data encoded for transmission over a digital telecommunication network describing analog signals representing application data and to transform or interpret said input as representative of application data in order to recover the application data.
The apparatus also comprises the communications hardware, memory, CPU and control logic to receive application data typically transmitted between applications through an analog MODEM and convert the data directly into digital data encoded for transmission over a digital telecommunication network describing analog signals representing application data.
The advantages accruing to the apparatus are apparent. In implementations which would presently require a MODEM and CODEC to facilitate data transmission, the apparatus of the present invention would eliminate the need for this additional hardware. Thus, the present invention performs the functions currently performed by a CODEC and a MODEM.
In some implementations, eliminating a MODEM avoids the use of limited expansion slots in a computer and allows the extra expansion slot to be used by additional resources. In addition, because employing the control logic allows data transmissions to flow directly between the communications interface device and the computer, the transmission is more efficient.
The advantages of the present invention are also apparent with respect to implementations which utilize a MODEM pool. Using the method and apparatus of the present invention in conjunction with a switching station (i.e. a central office or a private branch exchange), a MODEM pool could be eliminated. In addition, a variety of MODEM types could be represented in such an implementation. Furthermore, the functionality of the apparatus could be easily altered for a multitude of users simply by updating the control logic at the switching station.